Pediatric cystic diseases of the kidney

Abstract

Pediatric renal cystic diseases include a variety of hereditary or non-hereditary conditions. Numerous classifications exist and new data are continuously published. Ultrasound is the primary technique for evaluating kidneys in children: conventional and high-resolution US allows a detailed visualization of renal parenchyma and of number, size and location of the cysts, hence representing the most important diagnostic imaging technique for the first diagnosis and follow-up of these young patients. The purpose of this pictorial essay is to review the spectrum of renal cystic lesions in children from simple, complex or malignant single cysts to the several poly/multicystic kidney diseases.

Keywords: Cystic renal disease; Kidney; Neonatal; Pediatric; Ultrasound.

Fig. 1

Normal kidney (a) and two different aspects of dysplastic kidney (b, c)

Fig. 2

Examples of various cortico-medullary differentiations in cystic renal diseases

Fig. 3

Different localization of cysts: subcortical (a), cortico-medullary (b) and medullary (c)

Fig. 4

Simple cysts: US and color Doppler typical aspects

Fig. 5

Caliceal diverticulum: anechoic round lesion at the upper pole of the kidney with fortuitous evidence of a connection with a calyx (yellow double arrow)

Fig. 6

Venous and delayed CT phases (a): presence of iodinated urine inside the ‘cystic lesion’ allows the diagnosis of caliceal diverticulum at the upper pole. Delayed MR phase of two different patients (b): a simple cyst homogenously hypodense and a caliceal diverticulum partially filled with enhancing urine (white arrow)

Fig. 7

Bosniak III–IV cystic lesions: wall thickening, parietal nodule and a septum with nodule

Fig. 8

A septate renal cyst at US evaluation and its simple appearance at multiphasic CT

Fig. 9

Two examples of cystic pediatric renal tumors: US and MR appearance

Fig. 10

MCDK: multiple cysts of variable size and dysplastic residual parenchyma in a central position

Fig. 11

MCDK: US scan at diagnosis (a), check scans demonstrating compensatory hypertrophy of contralateral kidney (b) and involution of the affected kidney (c)

Fig. 12

Two cases of segmental MCDK associated with duplicated collecting system: isolated multicystic dysplasia in upper pole (a) and multicystic dysplasia in upper pole associated with dysplastic kidney (b)

Fig. 13

Acquired renal cysts. Patient with left-sided duplicated collecting system and ureteral ectopic insertion in vagina: coronal T2w image demonstrates severe upper ureteral dilatation associated with multiple tiny cysts with peripheral distribution at upper moiety. US depicts hydronephrosis and thinned dysplastic renal parenchyma with small peripheral cysts

Fig. 14

Acquired renal cysts. Retrograde cystography demonstrates bilateral refluent megaureter. US depicts severe pyelic dilatation and thinned dysplastic hyperechoic renal parenchyma with small peripheral cysts

Fig. 15

ARPKD: anteroposterior x-ray depicts pulmonary hypo/dysplasia, centralization of bowel associated with bulging flanks due to enlarged kidneys. US confirms nephromegaly, and high-resolution US allows the identification of linear cystic cortico-medullary microdilatations

Fig. 16

High-frequency US in ARPKD: multiple hyperechogenic dots with “comet-tail” reverb and some macroscopic cysts between countless tiny microcysts in a radial distribution representing dilated tubules

Fig. 17

US image of the liver in a child affected by ARPKD reveals hepatopathy and Caroli disease with extensive cystic biliary dilatation

Fig. 18

ADPKD: small cortical and medullary cysts overlapping parenchyma with normal US appearance

Fig. 19

NPHP: US depicts diffusely increased echogenicity of the renal parenchyma with loss/poor cortico-medullary differentiation, cysts, if present, affect the medulla as well as the cortico-medullary junction

Fig. 20

Tuberous sclerosis: US shows combination of multiple hyperechoic angiomyolipomas and isolated small cysts